A small task for viva prep: book an hour or two in your diary to check recent publications.
Check journals you have read in the past, ask your supervisors and visit pre-print servers if appropriate to see if there is anything interesting you have missed in the months leading up to submission. It would be natural to be unaware of something if your focus is mostly on getting your thesis written up. Now you can take a short period to check if there’s anything relevant to your interests.
Your goal is not to find more material for your thesis. Your thesis, with the exception of amendments, is done. The purpose is to show your examiners – and yourself – that you are a good, capable researcher.
An hour or two after submission, sometime in the weeks leading up to the viva, can be enough to get up to date.